Purchased a Grapevine at Costco in N. CA recently? Read This!

Alert and photo from UC IPM

An invasive insect called the glassy-winged sharpshooter (GWSS) has been found on grapevine shipments sold at select Costco locations in Northern California between April 21 and May 19, 2026.

If you or someone you know has recently purchased a grape plant at Costco please read this article to know what to do, what NOT to do, and help spread the word to limit the spread of the insect and the disease it carries.



GWSS is an invasive insect pest that spreads a bacterium which causes a fatal grapevine disease (called Pierce’s disease), potentially affecting California vineyards. The pest can also damage citrus trees, landscape plants and other crops. Early detection and rapid response are critical to preventing the pest from spreading further.

State and local agricultural officials identified the issue quickly and immediately began response and containment efforts. The infested nursery stock came from a nursery in Fresno. Fresno County Agricultural Commissioner staff and CDFA personnel have been working on-site since May 19^th to stop shipments, investigate the situation, and determine corrective actions.

Costco has been cooperative in notifying customers, issuing refunds and helping connect purchasers with local county agricultural commissioner offices for inspection and disposal guidance.

WHAT TO DO IF YOU PURCHASED A PLANT

People who purchased a grapevine from Costco in an affected county between April 21 and May 19, should take the following steps:

• Isolate the plant:
• Keep the plant in its original pot or container and away from other plants.
• Do not put the plant in the ground if you have not already done so.
• If possible, place the plant(s) in two trash bags, one inside the other, and seal them closed.
• Do not return, transport or relocate the plant. 
• Do not place the plant in the trash or compost bin.
• Contact your local County Agricultural Commissioner’s Office right away:
• An agricultural inspector will come to look at the plant and other nearby host plants.
• If inspectors find GWSS on the grapevine, they will safely remove and dispose of the plant.
• GWSS monitoring traps may be placed on the property.
• Please cooperate with local inspectors if they need to investigate plants on your property.
• Please help spread the word. Share this notice on your social media, local networks, or simply talk to your neighbors and friends.

For more information visit the California Department of Food and Agriculture.

Notes From My Garden - Down the Scented Garden Path

Joy Sakai, UC Master Gardener, Yolo County

In the early 1900s a subtle way of warning a naive young person to avoid being misled or put in a “compromising position” was “Don’t be led down the garden path!” Oh my! Prim matrons knew that gardens are a sensual experience (and the perfect place for romance). If you enjoy being quiet and observant in a garden, you already know they can stimulate all of our senses.

We might hear birdsong or the humming of insects, see brightly colored flowers being visited by equally bright butterflies, and we taste the succulent fruits of our labors. We feel the warmth of the sun, a cooling breeze, or the brush of leaves. The garden’s scents are what I find to be most enchanting. That is because the perfume of a garden is dispersed and floats on the air. Now you perceive it and the next moment you don’t. The source of a scent in a garden may not be immediately obvious; you may find yourself wandering around trying to identify it. Other aromas, however, may be immediately identifiable...

Fertilizer Use in the Garden

Caroline Gengo, UC Master Gardener, Yolo County

Plants make their own food through photosynthesis (converting water and carbon dioxide into sugar and oxygen using solar energy). When we fertilize a plant, we are adding specific nutrients to the plant’s environment to support growth or maintenance. Many of the fertilizers we buy include some combination of nitrogen (N), phosphorus (P), and potassium (K). Nitrogen supports healthy leaves, phosphorus supports healthy roots, and potassium supports flowers and fruits. Fertilizer packages are often labeled with the ratio of these three macro(large) nutrients as three numbers separated by dashes (nitrogen - phosphorus - potassium or N-P-K). For example, if the fertilizer bag in the illustration below was a one hundred pound bag, there would be ten pounds of nitrogen, five pounds of phosphorus, and five pounds of potassium with eighty pounds of filler.

The ratio of N-P-K in a fertilizer impacts how the plant will respond. At the beginning of the season, when plants are just starting to grow and root and leaf development is key, higher proportions of N and P may be most beneficial. Later in the season, when flowers and fruit are...

Global Impacts of Growing at Home -

Soil Health as a Foundation to Global Sustainability (Part 1)

Kelly Mae Heroux, UC Master Gardener, Yolo County

When thinking about health, many of us think first about our bodies. We understand a healthy diet, physical activity, and quality sleep to be main pillars of health. But another kind of health is foundational to our own well-being, and it so often goes unnoticed: soil health!

Soil health is defined by the USDA as the capacity of soil to function as a living ecosystem that sustains plants, animals, and ultimately, us. Many people underestimate how deeply soil health impacts daily life, especially in urban and home settings. In fact, the health of our soils is closely tied to many of the biggest challenges facing the world today. The United Nations’ Sustainable Development Goals (SDGs) are seventeen global goals adopted by nearly all the countries in the world. They represent the United Nations member states’ most urgent social, environmental, and economic challenges.

Soils are a foundational but often hidden or understated component of many Sustainable Development Goals. In fact, soils can be connected to every single goal, linking what happens in our backyards and...

Ask a Master Gardener

This column is written by the Master Gardeners of Yolo County each month. It provides answers to selected questions recently asked by Yolo County gardeners..

This two question article previously appeared in the Winters Express and Davis Enterprise.

Have a gardening question? Send it to jmbaumbach@ucanr.edu, with “Ask MGs” in the subject line. Include as much detail as possible and pictures if you have them.

Phone illustration by ijmaki on Pixabay

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Peg Smith, UC Master Gardener, Yolo County

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Peg Smith, UC Master Gardener, Yolo County

June heat can be unpredictable. If you have recent transplants and temperatures soar, shade the transplants through the intense heat. As summer heat sets in, adjust irrigation as needed to deliver deep soakings to the vegetables at regular intervals. Mulch vegetables to conserve water, cool plant roots, and control weeds. In heatwave conditions shade....

University of California Statewide Integrated Pest Management Program

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